Mandy Moore 'Can't Wrap My Head Around' Being Married

She's come a long way from her days belting out bubblegum hits like "Candy," touring with the Backstreet Boys and dating Wilmer Valderrama. But sometimes even Mandy Moore can't believe she's all grown-up!

"Marriage is such a mark of adulthood in my mind," Moore, 25, tells PEOPLE. "It still feels not entirely real. Things are wonderful, and there's such a peaceful settledness about it. But sometimes I can't wrap my head around it. It seems bizarre but really cool at the same time, like, 'Wow – I did that!' "

Moore married singer-songwriter Ryan Adams, 34, on March 10 in Savannah, Ga., in a top-secret, low-key ceremony that she calls "quirky and random."

"I'm enjoying life, but I was enjoying it before [marriage] too," Moore says. "It's not like, 'Oh, my life is complete now.' I just have this extra incredible bonus of my best friend in the whole world, getting to spend every day with him."

Making The Album

Moore has another reason to celebrate: the May 26 release of her eighth album, Amanda Leigh. Recorded with vintage instruments and inspired by artists including the Paul McCartney and Fleetwood Mac, the album's '70s vibe took shape in less-than-glam conditions.

"We were in a drafty house near Boston in the dead of winter, eating bagels three meals a day," says Moore's producer and co-writer Mike Viola. "When people meet her, they go, 'Aww, she's super nice.' And she is. But she's tough as nails."

Moore, who's walked her share of red carpets, says she wouldn't have wanted it any other way: "I didn't have to wear make-up. I would stay in my PJs all day and just make music. It was awesome."

Her Early Years

Moore has worked steadily in music and film (starring in hits like 2007's License to Wed and the HBO series Entourage) ever since her debut album, So Real, put her on the map in 1999. Her early songs, she admits, still make her cringe.

"Anyone would be embarrassed of what they did at 15 or 16," she says. "I listen back to that first record and I'm like, 'Compared to what my contemporaries were doing, it was crappy.' You listen to an early Britney Spears or Christina Aguilera song, and they are great pop songs. I just don't feel like on that first record I got anywhere near anything great. But it was a fun place to start."

Growing up in the spotlight, Moore managed to stay grounded and avoid the pitfalls of fame. She credits a support system that included family, friends and her longtime professional team.

"I feel like it's a choice you make," she says of the fame game. "I was happy to kind of always scoot under the radar. That stuff never dazzled me."

Life with Ryan

These days Moore is content to make music (she's learning to play the bass guitar), walk her beloved Terrier mix Joni, nest at home in L.A. with Adams, and enjoy life's simple pleasures. "Jetlag haze+ garden walk+ chocolate shake+ love= perfection," she recently Tweeted.

"The unknown used to be really scary, just that fear of what's next? What if I'm not prepared?" she says. "I just don't feel that way anymore. I feel like the best is yet to come."

To check out her blog and hear samples from Amanda Leigh, check out Moore's Web site.